109142-59-8Relevant academic research and scientific papers
A Volumetric Study on the Thermal cis-to-trans Isomerization of 4-(Dimethylamino)-4'-nitroazobenzene and 4,4'-Bis(dialkylamino)azobenzenes: Evidence of an Inversion Mechanism
Nishimura, Norio,Tanaka, Tohru,Asano, Mari,Sueishi, Yoshimi
, p. 1839 - 1846 (2007/10/02)
The reaction volume (ΔV) for the thermal cis-to-trans isomerization of 4-(dimethylamino)-4'-nitroazobenzene in various solvents has been obtained by means of the photostationary state and capillary method.It has been shown that the activation volume (ΔV*) is closely related to the reaction volume in each solvent.Substantial kinetic pressure and solvent effects have been observed for 4,4'-bis(dimethylamino)azobenzene, 4,4'-bis(diethylamino)azobenzene, and 4,4'-(dipyrrolidin-1-yl)azobenzene.The ?-?* conjugation band of the trans-isomers of these compounds shows a remarkable solvatochromic shift, and logarithms of kinetic constants in various solvents are satisfactorily correlated with the Taft ?* scale, which represents solvent polarity-polarizability interactions.From McRae's formula, it has been deduced that the interaction between the solvent dipole and the solvent-induced dipole has an important influence on the behaviour of these 'push-pull' and 'push-push' azobenzenes.The results afford unequivocal evidence that the isomerization proceeds via a coplanar inversion transition state which is electronically similar to the trans-isomer.
